A conventional battery charger of this kind confirms earth leakage based on a leakage current value set by an earth leakage confirmation resistor and determined for every product (see, for example, Patent Document 1).
FIG. 4 is a block diagram of a conventional battery charger. As shown in FIG. 4, the conventional battery charger includes an earth leakage detector 11 for detecting earth leakage of the battery charger, an earth leakage circuit breaker 12 for switching energization of the battery charger from a commercially available external power source, an earth leakage confirmation relay 13 for switching an earth leakage confirmation circuit that is controlled by an ECU (electronic control unit) 15 provided on a side of a charging device to forcibly cause earth leakage in a circuit positioned downstream of the earth leakage detector 11, and an earth leakage confirmation resistor 14 for setting a current value to cause the earth leakage.    Patent Document 1: JP11-205909A